JP2002054708A - Screw shaft whirl-stop structure of screw jack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screw shaft whirl-stop structure of a screw jack having high rigidity and capable of exhibiting strong and excellent whirl-stop function to an impact load, and allowed to be adopted in a ball screw jack using the ball screw. SOLUTION: The screw jack 1 is provided with a main body case 2, a female screw body 11 rotatably provided on the main body case 2 to be driven to rotate by transmitting means 3, 4, a screw shaft 12 screw-engaged with the female screw body 11, to penetrate therethrough and reciprocated in the axial direction, and a protective tube 16 fixed to the main body case 2 to cover and protect the screw shaft 12 extended from the main body case 2. In the jack 1, the protective tube 16 is formed out of a square pipe, tie rods 19 are disposed along the inner four corners, a whirl-stop body 22 fixed to the rear end part of the screw shaft 12 is formed like a quadrangle fitted to the inner surface of the protective tube, and four corners of the whirl-stop body 22 are provided with cutout parts 25 engaged with the tie rods 19.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a female screw body rotatably provided in a main body case, wherein a screw shaft is screwed and penetrated.
The present invention relates to a screw jack detent structure for a screw jack in which the screw shaft reciprocates.

[0002]

2. Description of the Related Art In a screw jack of this type, a screw shaft is provided with a key groove formed on the outer peripheral surface of the screw shaft over the entire length of the screw shaft, and a key provided in a main body case is engaged with the key groove. The structure was generally used (see, for example, Japanese Utility Model Publication No. 2-11433).

[0003]

However, in the conventional anti-rotation structure described above, the keyway is formed on the outer peripheral surface of the screw shaft over the entire length. Removal of the burrs generated at the intersection with the screw thread is troublesome, not only is the processing cost high, but also the processing of the keyway makes the screw shaft easy to bend, and in particular the buckling strength is reduced. Was. In addition, the anti-rotation rigidity is determined by the surface pressure of the key engaged with the key groove, and the key cannot be so large. Therefore, the key groove may be locally expanded by an impact load. Further, since the keyway is machined across the thread of the screw shaft, the female screw surface of the female screw body with which the screw shaft is screwed is easily damaged, which adversely affects the life.

Further, in a screw jack using a ball screw and a ball nut for a screw shaft and a female screw body, a keyway cannot be formed in the ball screw shaft (which hinders the rolling operation of the ball). It has not been possible to employ a shaft detent structure.

The present invention has been made in view of the above-mentioned problems of the conventional screw shaft detent structure, and there is no need to machine a keyway over the entire length of the screw shaft. An object of the present invention is to provide a screw jack screw shaft detent structure that exhibits an excellent detent function and can be employed in a ball screw jack using a ball screw.

[0006]

The technical measures taken by the present invention to achieve the above object are as follows.

A main body case, a female screw body rotatably provided in the main body case, and rotationally driven by a transmission means;
A screw comprising: a screw shaft that is screwed into the female screw body, penetrates, and reciprocates in the axial direction; and a protection cylinder that is fixed to the main body case and covers and protects the screw shaft extending from the main body case. In the jack, the protection cylinder is formed by a square pipe, and tie rods are provided along four inner corners of the jack, and a rotation preventing body fixed to a rear end of the screw shaft fits an inner surface of the protection cylinder. It is characterized in that it is formed in a quadrangular shape, and is provided with cutouts that engage with the tie rods at four corners of the rotation preventing body.

[0008] As a preferred specific configuration of the transmission means, a worm housed in the main body case and a worm wheel meshing with the worm, the female threaded body having a screw shaft screwed to the worm wheel is penetrated. Are provided.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show a ball screw jack 1 having a screw shaft detent structure according to the present invention.
A worm speed reduction mechanism is used as the transmission means.

A worm 3 and a worm wheel 4 meshing with the worm 3 are rotatably supported and housed in the main body case 2. An input shaft 3a connected to the worm 3 protrudes from the main body case 2, and an electric motor or the like is provided. Is linked to the rotary driving device.

In the center of the worm wheel 4, an insertion hole 5 through which a ball screw shaft 12 to be described later penetrates is provided. A mounting flange 6 is provided at the rear end of the main body case 2, and a ball nut 11 described later is provided at the front end opening.
Is fixedly mounted. An oil seal 10 is provided at a boundary between the main body case 2 and the case cover 7.

The ball nut 11 has a ball guide groove 11a spirally formed on the inner peripheral surface of a cylindrical main body, and is integrally formed with the worm wheel 4 coaxially. The integrated worm wheel 4 and ball nut 11 are rotatably supported by the main body case 2 and the case cover 7 via bearings 8,8.

The ball screw shaft 12 is mounted on the worm wheel 4.
Through the insertion hole 5, and the guide groove 1 into the ball nut 11.
The guide bush 9, 9 is screwed through a large number of balls 13 fitted in 1a and fitted in the opening at the tip of the ball nut 11 and the rear end of the insertion hole 5 of the worm wheel 4.
It is slidably supported by. An operating screw portion 14 and a stopper 15 screwed to the screw portion 14 are provided at a distal end portion of the ball screw shaft 12 protruding forward from the case cover 7. Further, the rear half of the ball screw shaft 12 projects outward from the rear end opening of the main body case 2,
The main body case 2 is covered with a protection tube 16 fixedly protruding from the rear end thereof. The protection cylinder 16 is provided with a rotation preventing structure for the ball screw shaft 12.

As shown in FIGS. 3 and 4, the protective cylinder 16 is formed by a square pipe having a square cross section, and a flange plate 17 fixed to one end is fixed to a main body case by mounting bolts 18. 2 and is disposed coaxially with the ball screw shaft 12. In addition, four tie rods 19 are provided along the four inner corners of the protective cylinder 16, and each tie rod 19 is attached to the inner wall 16 of the protective cylinder 16.
a. One end of each tie rod 19 is screwed and fixed to the flange plate 17, and the other end is fixed to a cover plate 20 that covers a rear end opening of the protective cylinder 16 via a fastening nut 21.

On the other hand, a rotation preventing body 22 is fitted to the rear end of the ball screw shaft 12 via a key 23 so as not to rotate, and is fixed by a fixing nut 24. The detent body 22 is formed in a square shape that fits the inner surface of the protection cylinder 16, and has cutouts 25 that engage with the tie rods 19 at the four corners. The rotation of the ball screw shaft 12 is prevented by the rotation preventing body 22 having such a structure, and the rotation preventing body 22 is guided by the four tie rods 19 supported inside the protective cylinder 16 and is axially moved. By sliding, a detent mechanism having high rigidity and strong against an impact load is configured, and the ball screw shaft 12 can smoothly reciprocate in the protective cylinder 16.

Next, a notch 25 provided in the rotation preventing body 22
Will be described. As shown in FIG.
5 is formed by two planes 26 that intersect at right angles, the notch 25 can be easily machined and the sliding resistance against the tie rod 19 is small. When torque acts, there is a disadvantage that the sliding resistance increases. On the other hand, as shown in FIG. 6, if the notched portion 25 is formed by an arc-shaped curved surface 27 that contacts the outer peripheral surface of the tie rod 19, machining is difficult, but the contact pressure on the tie rod 19 is low. Even if a large torque acts on the screw shaft 12, the screw shaft 12 can slide smoothly.

In the above embodiment, the worm screw jack 1 using the ball nut 11 and the ball screw shaft 12 has been described.
The thread of the threaded shaft threaded into the female threaded body may be a trapezoidal thread or another thread shape.

[0019]

As described above, the screw shaft detent structure according to the present invention has a high rigidity and a detent function that is strong against an impact load. In particular, since it is not necessary to machine a keyway extending over the entire length of the screw shaft as in the related art, it is suitable for a screw shaft rotation preventing structure of a ball screw jack using a ball screw that cannot perform such keyway machining. .

[Brief description of the drawings]

FIG. 1 is a partially longitudinal front view of a ball screw jack provided with a screw shaft detent structure according to the present invention.

FIG. 2 is a left side view of the same section.

FIG. 3 is a sectional view taken along line 3-3 in FIG. 1;

FIG. 4 is a sectional view taken along line 4-4 in FIG. 1;

FIG. 5 is a front view of the detent body.

FIG. 6 is a front view showing another embodiment of the detent body.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ball screw jack 2 Main body case 3 Worm 4 Worm wheel 5 Insertion hole 7 Case cover 8 Bearing 9 Guide bush 11 Ball nut 12 Ball screw shaft 13 Ball 16 Protective cylinder 19 Tie rod 22 Non-rotating body 25 Missing part

Claims (3)

[Claims] 1. A main body case, a female screw body rotatably provided in the main body case and driven to rotate by a transmission means, and a screw shaft screwed into the female screw body, penetrating therethrough, and reciprocating in the axial direction. A protection cylinder fixed to the main body case and covering and protecting the screw shaft extending from the main body case, wherein the protection cylinder is formed by a square pipe, and tie rods are formed along four inner corners thereof. Is provided, and a rotation stopper fixed to the rear end of the screw shaft is formed in a square shape that fits the inner surface of the protective cylinder,
A screw shaft detent structure for a screw jack, wherein notch portions for engaging with the tie rods are provided at four corners of the detent body. 2. The structure according to claim 1, wherein the female screw body is a ball nut, and the screw shaft is a ball screw. 3. The worm wheel according to claim 1, wherein the transmission means comprises a worm housed in the main body case, and a worm wheel meshing with the worm, and the female screw body is provided through the worm wheel. 2. The screw shaft detent structure of the screw jack described in 2.